Golden Days. Hana to Yume, 8 volumes. Mitsuya time slips back to Tokyo of 1921 to do something his dying grandfather regretted his whole life... save his best friend Jin from... spoiler city if say more. Ivyscan only gotten to Ch26 (Vol5) so far.

Keep hoping an English company will licence the manga at least if it never gets made into an anime.

I haven't read too much manga yet, but I'd say Life is Money or Sugar Dark. They were pretty darn awesome. :3
And this thread reminded me to check on my manga list. 2 are updated. Tis time to read some manga. >:D